1. Field of the Invention
This invention relates to a semiconductor module and a method of mounting a semiconductor laser element on the semiconductor module.
2. Description of the Related Art
As is well known, an optical pickup for reading information recorded on an optical disks, such as a CD and DVD, can optically read the information such that a laser beam emitted from a semiconductor laser element, which serves as a light source, disposed in a main body, is guided to an objective lens along an optical path of a predetermined optical system made up of various optical components. A light beam gathered by the objective lens is then projected onto the information recording surface of the optical disk, reflected light that has undergone light modulation according to the recorded information of the optical disk is then generated. The reflected light is then guided again through the objective lens to a light receiving element along a predetermined optical path, and, based on the output of received light, the light receiving element generates a signal according to the recorded information of the optical disk.
In an optical pickup such as this, in order to read recorded information of the optical disk accurately, it is required that a laser beam of a predetermined wavelength emitted from the semiconductor laser element be caused to, without being out of alignment with an optical axis, fall upon the predetermined optical system and generate a light beam by the light gathering of the objective lens, and the light beam be focused at an appropriate position on the information recording surface of the optical disk. To do so, the semiconductor laser element must be disposed so to have no axial deviation with respect to the optical system and take an appropriate position in the axial direction of the laser beam with respect to the predetermined optical system.
If the semiconductor laser element is not disposed properly with respect to the optical system, the laser beam is made incident in a deviated state of the optical axis of the laser beam with respect to the optical axis of the optical system. Accordingly, the incident position of the light beam on the information recording surface or the incident angle of the light beam deviates from an allowable range, so that reflected light does not undergo accurate light modulation by recorded information, and the incident position of the obtained reflected light on the light receiving element deviates greatly. As a result, it is impossible not only to obtain a sufficient amount of reflected light but also to allow the reflected light to undergo accurate light modulation according to recorded information. This often makes it impossible to accurately read the recorded information by means of the reflected light.
Therefore, in the optical pickup, some optical components, which are to be disposed beforehand at predetermined positions in the main body, are each fixed at a predetermined position in the main body properly, and the semiconductor laser element is mounted in the body so as to be positionally adjustable with respect to the optical system made up of the optical components, and, thereafter, the optical position of the semiconductor laser element is adjusted with respect to the optical system.
The semiconductor laser element is inserted into a holding hole formed in, for example, a heat radiation member made of a material that has heat radiating properties as if the laser element is dropped thereinto, and the heat radiation member is mounted in a main body in a state in which the laser element is held in the heat radiation member while being pressed by, for example, a leaf spring. By moving the semiconductor laser element with respect to the pressing leaf spring, positional adjustment can be made in a planar direction (x-y axis direction) perpendicular to an axial direction (z axis direction) of the laser beam emitted from the semiconductor laser element.
The heat radiation member for holding the semiconductor laser element is held in the main body, and is mounted to be movable and adjustable in the direction of the optical axis (z axis direction) of the laser beam emitted from the semiconductor laser element with respect to a case. The positional adjustment in the directions of the three axes (x axis, y axis and z axis) is repeatedly carried out for each axial direction by the use of an adjusting fixture, and, thereby, the positional adjustment of the semiconductor laser element with respect to the heat radiation member and the positional adjustment of the heat radiation member with respect to the case are carried out, and, as a result, the adjustment of the optical position of the semiconductor laser element is carried out.
In order to adjust the optical position of the semiconductor laser element of the conventional optical pickup, in addition to the adjusting method carried out by arranging the optical components as mentioned above, there is another adjusting method in which, for example, the semiconductor laser element is mounted to be movable and adjustable in the directions of two axes (x axis and y axis) with respect to the pickup body, and the light receiving element (PD) among the other optical systems is mounted to be movable and adjustable in the axial direction (z axis direction) of the laser beam. In this method, the positional adjustment of the laser beam in the directions of the three axes (x axis, y axis, and z axis) is carried out by repeatedly carrying out the axial adjustment (x-y adjustment) of the semiconductor laser element and the axial adjustment (z adjustment) of the light receiving element (PD).
As mentioned above, the adjustment of the optical position of the laser beam of the semiconductor laser element must be repeatedly carried out in the direction of each axis after the semiconductor laser element, the light receiving element, etc., are temporarily mounted in the case. Therefore, much time is consumed to complete the adjustment of the optical position thereof.
The present invention was made in consideration of the above problem, and it is an object of the present invention to provide a semiconductor module capable of mounting a semiconductor laser element promptly and reliably at a predetermined optical position with respect to an optical system formed in the case of a semiconductor module and provide a mounting method of the semiconductor laser element of the semiconductor module.
According to a first aspect of the present invention, a semiconductor module comprises a semiconductor laser element; a holding member for fixedly holding the semiconductor laser element, the holding member having thermal conductivity; a base member for fixedly holding the holding member, the base member having thermal conductivity; and a case for fixedly holding the base member; in which a laser beam emitted from the semiconductor laser element is guided to a predetermined optical system disposed in the case and is projected out of the semiconductor module, and by fixing the holding member that fixedly holds the semiconductor laser element to the base member by means of a thermal type adhesive member that has thermal conductivity, the semiconductor laser element is fixed at a predetermined optical position where optical adjustment with respect to the optical system has been carried out.
In the semiconductor module according to the first aspect of the present invention, the semiconductor laser element can be promptly and reliably mounted at the predetermined optical position where optical adjustment with respect to the optical system of the case has been carried out, and, after mounting the semiconductor laser element, there is no need to adjust the optical position of the laser beam of the semiconductor laser element.
Further, in the semiconductor module according to the first aspect of the present invention, since the semiconductor laser element, the holding member, the adhesive member, and the base member make up a thermal path that has thermal conductivity, the heat generated when the semiconductor laser element emits a laser beam can be promptly transmitted to the base member. Accordingly, heat does not accumulate in the semiconductor laser element, and the operation of the semiconductor laser element becomes stable. Therefore, the life of the semiconductor laser element is not shortened.
According to a second aspect of the present invention, a semiconductor module comprises a plurality of semiconductor laser elements; a plurality of holding members for fixedly holding the plurality of semiconductor laser elements individually, the plurality of holding members having thermal conductivity; a plurality of base members for fixedly holding the plurality of holding members individually, the plurality of base members having thermal conductivity; and a case for fixedly holding the plurality of base members; in which laser beams emitted from the plurality of semiconductor laser elements are guided to an optical system formed by optical components disposed in the case and is projected out of the semiconductor module, and, by fixing the plurality of holding members that fixedly hold the plurality of semiconductor laser elements, respectively, to the plurality of base members, respectively, by means of a thermal type adhesive member that has thermal conductivity, the plurality of semiconductor laser elements are fixed at predetermined optical positions where optical adjustment with respect to the optical system has been carried out.
In the semiconductor module according to the second aspect of the present invention, the plurality of semiconductor laser elements can be promptly and reliably mounted at the predetermined optical positions where optical adjustment with respect to the optical system of the case has been carried out, and, after mounting the semiconductor laser elements, there is no need to adjust the optical positions of the laser beams of the semiconductor laser elements.
Further, in the semiconductor module according to the second aspect of the present invention, since the semiconductor laser elements, the holding members, the adhesive members, and the base members make up a thermal path that has thermal conductivity for each semiconductor laser element, the heat generated when the semiconductor laser elements emit laser beams can be promptly transmitted to the base member belonging to each thermal path. Accordingly, heat does not accumulate in each semiconductor laser element, and the operation of each semiconductor laser element becomes stable. Therefore, the life of each semiconductor laser element is not shortened.
According to a third aspect of the present invention, in the semiconductor module according to the first or second aspect of the present invention, the base member is fixedly held by the case in a state in which at least a part of the base member is exposed to the outside of the case.
According to the third aspect of the present invention, the heat generated when the semiconductor laser element emits a laser beam is transmitted to the base member belonging to the related thermal path, and, thereafter, the heat is efficiently radiated from the bare part of the base member outwardly. Accordingly, heat does not accumulate in the semiconductor laser element, and the operation of the semiconductor laser element becomes stable. Therefore, the life of the semiconductor laser element is not shortened.
According to a fourth aspect of the present invention, in the semiconductor module according to the third aspect of the present invention, the base member is greater in thermal conductivity than the case.
According to the fourth aspect of the present invention, the heat generated when the semiconductor laser element emits a laser beam is transmitted to the base member belonging to the related thermal path, and, thereafter, the heat is efficiently radiated from the bare part of the base member outwardly without diffusion into the case. Accordingly, heat does not accumulate in the semiconductor laser element, and the operation of the semiconductor laser element becomes stable. Therefore, the life of the semiconductor laser element is not shortened.
According to a fifth aspect of the present invention, in a mounting method of a semiconductor laser element of a semiconductor module for mounting the semiconductor laser element at an optical position where predetermined optical adjustment has been carried out with respect to an optical system formed by optical components disposed in a case of the semiconductor module, the mounting method comprises a first step of positioning the semiconductor laser element fixedly held by a holding member that has thermal conductivity at the optical position where the predetermined optical adjustment has been carried out with respect to the optical system formed by the optical components disposed in the case of the semiconductor module; a second step of heating a base member that is fixedly held by the case and has thermal conductivity; and a third step of fixing the holding member that fixedly holds the semiconductor laser element to the heated base member by means of a thermal type adhesive member that has thermal conductivity; in which, by fixing the base member to the heated base member in a state in which the semiconductor laser element held by the holding member is disposed at the optical position determined by the positioning in the third step, an optical axis of the semiconductor laser element is adjusted and the holding member is fixedly mounted at the predetermined optical position of the case with respect to the optical system.
According to the fifth aspect of the present invention, the semiconductor laser element can be promptly and reliably mounted at the predetermined optical position where optical adjustment with respect to the optical system of the case has been carried out, and, after mounting the semiconductor laser element, there is no need to adjust the optical position of the laser beam of the semiconductor laser element.
According to a sixth aspect of the present invention, in a method of mounting semiconductor laser elements of a semiconductor module for mounting the plurality of semiconductor laser elements at optical positions where predetermined optical adjustment has been carried out with respect to an optical system formed by optical components disposed in a case of, the semiconductor module, the mounting method comprises a first step of positioning one of the plurality of semiconductor laser elements fixedly held by a holding member that has thermal conductivity at one of the optical positions where the predetermined optical adjustment has been carried out with respect to the optical system formed by the optical components disposed in the case of the semiconductor module; a second step of heating a base member that is fixedly held by the case and has thermal conductivity; and a third step of fixing the holding member that fixedly holds the one of the plurality of semiconductor laser elements to the heated base member by means of a thermal type adhesive member that has thermal conductivity; in which, by fixing the holding member to the heated base mender in a state in which the one of the plurality of semiconductor laser elements held by the holding member is disposed at the one of the optical positions determined by the positioning in the third step, an optical axis of one of the plurality of semiconductor laser elements is adjusted and the holding member is fixedly mounted at the predetermined optical position of the case with respect to the optical system, and by sequentially and repeatedly performing the first, second, and third steps for the plurality of semiconductor laser elements, the plurality of semiconductor laser elements are mounted at optical positions, respectively, where predetermined optical adjustment has been carried out.
According to the sixth aspect of the present invention, the semiconductor laser elements can be promptly and reliably mounted at the predetermined optical positions where optical adjustment with respect to the optical system of the case has been carried out, and, after mounting the semiconductor laser elements, there is no need to adjust the optical positions of the laser beams of the semiconductor laser elements.
According to a seventh aspect of the present invention, in the mounting method according to the fifth or sixth aspect of the present invention, the base member is fixed to the case in a state in which at least a part of the base member is exposed to the outside of the case, and the heating of the base member in the second step is carried out such that the bare part of the base member is heated from the outside.
According to the seventh aspect of the present invention, the thermal type adhesive member placed on the base member that has thermal conductivity can be promptly and reliably heated by heating the bare part of the base member that has thermal conductivity, and, therefore, the holding member can be promptly and reliably fixed to the base member.
According to an eighth aspect of the present invention, the base member having a thermal conductivity is greater than that of the case is used in the third step of the mounting method according to the seventh aspect of the present invention.
According to the eighth aspect of the present invention, since the heat of the base member does not diffuse into the case when the bare part of the base member having a thermal conductivity is greater than that of the case is heated, the thermal type adhesive member placed on the base member that has thermal conductivity can be promptly and reliably heated, and, therefore, the holding member can be promptly and reliably fixed to the base member.